There are a number of different devices and methods for measuring, calculating or estimating the heart rate of a person. Heart rate monitors and similar wristop computers may, for example, include a transmitter belt attached to the human body by a flexible belt, which nowadays typically measures the pulse. The term heart rate monitor refers to a wristop computer or some other corresponding device, equipped with heart rate monitor properties. Such heart rate measurement may e.g. take place during motion of the person. The measuring device equipped with electrodes transmits measurement data wirelessly to e.g. a wristwatch-like wristop computer, in which at least a part of the received signal is processed and displayed on the display of the wristop computer. The pulse data of the person may be also stored on said wristop computer. Known wristop computers can be used to measure not only pulse, but also, for example, blood pressure, speed, acceleration, distance traveled, and direction data.
With regards to pulse measurement, one or more sensors may be positioned against the chest, neck, wrist, auricle or foot of a person. Portable devices that measure the heart beats may make use of a chest belt or a wrist watch, for instance. The devices measure the electric signal of the heart (ECG), for example during the person's physical activity. The electrical activity of the heart is measured over a period of time using electrodes placed on the skin of the person. Documents U.S. D739,944 S, U.S. D739,943 S, and U.S. D676,137 S for example illustrate different heart rate belts.
The measurement information is typically transmitted from the heart rate belt to the wristop computer wirelessly. If several persons using wristop computers are close to each other, the receiver must identify the correct transmitter. In newer devices, digital signal transfer with digital identification codes has been used, for instance. In this solution, the transmitter belt includes a set of circuits, which are used to detect the heartbeats and create pulse-interval information, which states the length of time between the detected heartbeats. The pulse-interval data is coded into a digital signal, which is transmitted to the wristop computer. Subsequently, the pulse-interval data may be analysed by the wristop computer prior to displaying the pulse data on the display of the wristop computer. Additionally or instead, the pulse data of the person may be stored on said wristop computer.
Certain devices for heart rate monitoring measure a sufficient amount of data to form a wave form of a pulse and other devices only measure the time interval between two consecutive heartbeats, i.e. the pulse-interval data. Systems providing a wave form of a pulse have to process and/or store more data than systems providing only pulse-interval data. However, systems providing a wave form of a pulse may be of more use e.g. for a doctor or other medical personal for a diagnosis after reading out the memory.
Of course, energy consumption takes place by means of such measurement, analysis, and storing of pulse data. Consequently, portable measurement devices are equipped with at least one power source such as a battery. Systems providing a wave form of a pulse consume more energy than systems providing only pulse-interval data, since continuous measurement of the electric signal of the heart is required for measuring a wave form of a pulse. Further, for both different systems a sufficient memory has to be provided in order to store the pulse data by means of the wristop computer.
In view of the foregoing, it would be beneficial to provide a system for heart rate monitoring of an object, which system is able to reduce energy consumption during measurement of the heart beats and/or is able to reduce required memory.
An example of a heart rate monitor is disclosed in Document U.S. Pat. No. 9,167,975 B1. The document discloses a motion resistant device to monitor heart rate in ambulatory patients. The device allows for a continuous heart rate to be collected and recorded for extended time frames equivalent to a Holter monitor or special pulse oximeter.
Documents U.S. Pat. No. 9,179,849 B1 and U.S. Pat. No. 9,314,174 B1 describe a mobile plethysmographic device for detecting a premature ventricular contraction event. The mobile plethysmographic device generates a pleth waveform, which is automatically screened by algorithms that measure the waveform to correlate, detect and store aberrations related to heart anomalities. A premature ventricular contraction event for a patient is determined based on an identification of a time interval of the pleth waveform that is below the threshold minimum time interval followed immediately by a time interval that is above the threshold maximum tine interval.
Documents U.S. Pat. No. 9,144,385 B1 and U.S. Pat. No. 8,974,396 B1 teach a mobile plethysmographic device for detecting a premature atrial contraction event. The mobile plethysmographic device generates a pleth waveform, which is automatically screened by algorithms that measure the waveform to correlate, detect and store aberrations related to heart anomalies. A premature atrial contraction event for a patient is determined based on an identification of a time interval of the pleth waveform that is below the threshold minimum time interval followed immediately by a time interval that is above the threshold maximum tine interval.